A Review of the Performance of Extrinsically Powered Prosthetic Hands

Extrinsically powered prosthetic hands offer the potential to replicate the capabilities of a human hand and thus enable an upper limb amputee to complete activities of daily living. Over the past 20 years however, amputees have consistently indicated that several user needs have not been met. Many of these user needs are related to the hardware of the prosthetic hand, and in particular, its actuators and transmissions. These needs include reduced weight and improved dexterity, hand speed, hand strength, and functionality. To understand why these user needs have not been adequately addressed, we first seek to investigate the state of the art in extrinsically powered prosthetic hands through a comprehensive review of the research, commercial, and open-source literature. This review focuses specifically on actuation of the prosthetic hands because actuation is central to addressing the above user needs. This review, based on actuation strategies, enables a characterization and exploration of the actuation design space. We also compare the performance of the reviewed prosthetic hands with both the human hand and ideal recommendations for prosthetic hands to conclude that existing prosthetic hands do not adequately address user needs. This systematic characterization of the actuation design space helps identify that improvements to transmission pathways are the most promising avenue of further research and innovation to enable future prosthetic hands that adequately address user needs.